1. Field of the Invention
Embodiments of the present invention relate, generally, to a phosphor paste composition comprising phosphate ester as a dispersant, and a display device using the same. More particularly, embodiments of the present invention relate to a novel phosphor paste composition, in which phosphate ester is used as a dispersant to increase the loading amount of a phosphor without greatly increasing the viscosity thereof, thus improving luminance and maintaining excellent workability, and to a display device using the phosphor paste composition.
2. Description of the Related Art
Recently, display devices have been developed from conventional cathode ray tubes (CRTs) to plasma display panels (PDPs), liquid crystal displays (LCDs) or field emission displays (FEDs) having various applications. Such display devices have a phosphor screen in common.
The PDP, which is receiving emphasis as a flat panel display device for future use as a digital imaging display, is a display for realizing an image by exciting a phosphor screen using UV light emitted upon electrical discharge by a gas. The quality of the PDP depends on the phosphor screen. That is, even though the phosphor itself has high luminance, if the phosphor screen is not formed as desired, the PDP does not exhibit high luminance.
Typically, the phosphor screen is prepared by uniformly applying a phosphor paste composition on a substrate and then drying it. The phosphor paste composition is composed mainly of a solvent, a binder, and a phosphor, and further includes a dispersant to improve the dispersibility of the phosphor, if necessary.
Conventionally, phosphor pastes have had no dispersant, or have frequently used carboxylic acid as a dispersant. However, such a conventional phosphor paste having no dispersant or having carboxylic acid as a dispersant is disadvantageous because the decrease in viscosity is insignificant, and thus, the loading amount of the phosphor becomes small.
Also, the phosphor included in the phosphor paste is formed mainly of inorganic material. Hence, if the loading amount of the phosphor is increased, the viscosity is also increased, and the phosphor screen is difficult to make uniform, resulting in reduced workability. Consequently, productivity is lowered.
In this regard, Korean Patent Laid-open Publication No. 2001-96586 discloses a phosphor paste composition and a phosphor screen using the same, in which phosphate ester represented by Formula 1, below, is used as a dispersant.

However, the phosphate ester used as a dispersant in the above patent is an alkylester of alkylphosphonic acid, which is typically exemplified by methylester of 1-tetradecane phosphonic acid (TDPA) having a low molecular weight of 278.37 and a relatively short tail. Although the dispersant disclosed in the above publication may more efficiently disperse the phosphor than many other conventional dispersants, the dispersibility thereof is still unsatisfactory.
Therefore, there is urgent need for the development of a phosphor paste, which enables an increase in the loading amount of the phosphor and the exhibition of excellent workability, in order to realize a phosphor screen having high luminance.